This invention relates to a technique of archiving in a storage system, and more particularly, to a technique of enhancing the security and performance of a storage subsystem.
The recent improvements in computer performance and Internet line speed have caused an increase in amount of data handled by a computer. There is also a growing expectation for archive systems which keep files in storage subsystems for a long period of time as a way to meet legal regulations or as a preparation for possible lawsuits.
JP 2004-509415 A discloses a technique of improving the file retrieval speed by indexing files based on the files' attribute information or the like, and thus speeding up access to stored files.
The technique disclosed in JP 2004-509415 A creates an index containing an update time, or a rank for determining in what order documents are to be displayed, and a text extracted from a search object file. In the case where a search object file contains confidential information such as a customer name, the search object file is encrypted and the encrypted search object file is stored in a storage subsystem. However, encrypting a search object file does not eliminate the risk of a leak of confidential information since a text extracted from the search object file is used to create a plaintext index and confidential information could be obtained from the created index.
A leak of information from an index can be prevented by encrypting the created index before storing the index.